Method and apparatus for pressing, deaerating, and drying



April 2, 1946. c. w. wlLLiA'Ms 2,397,827

METHOD AND'APPARATUS FOR PRESSING, DEAERATING, AND DRYING I Filed May25, 1942 ,11% 107m/@5 wv wf//fnms Premessa-.2, 194s r' FFICIl-.

' uarnon Ann Arrmrvs Fon raasslNG. nnanaarma, AND Dama charte w.william., Louisville, xy. Application May 25. 1942, serial' No. 444,340

1 (o1.v i1-sa) subject, each plate being exposed through a standardcolor nlter, i. e. red, yellow or blue. A black and white printis madefrom each of the negatives on bromide paper. The bromide prints arecontacted with so-called carbon tissues (red, yellow and blue) whichhave pigmented gelatin on their surfaces. In each case the bromideprint, in conjunction with a sensitizer previously soaked into thepigmented gelatin, acts to form a hardened image on the colored gelatinwhich is identical to the image on the bromide print.. The bromide printis removed from the pigment tissue and the latter pressed onto a sheetof smooth plastic material on which it is washed in hot water to removethe soft gelatin, leaving the hardened image. After the three coloredimages have been thus secured on three plastic sheets, they are,transferred individually to a single temporary supporting sheet inregistry and subsequently -to a sheet oi paper to make the final print.

In the step of applying the pigment tissue to the sheet of plastic,considerable dimculty has been encountered and much time has been wasteddue to the inclusion of air bubbles between the contacting surfaces ofthe sheets, and air apparently included in the gelatin layer, and thenecessity for removing these air bubbles. -The existence of the airbubbles or pockets -becomes particularly noticeable when the pigmentsheets are immersed in warm water. as is necessary in the processing,because of the expansion of the air under the increased temperature. Ifthe air bubbles are not removed, they cause imperfections in the ilnalprint.

Heretofore it has been the practice to squeegee the plastic sheet andthe pigment sheet vigorously for an extended period of time in an effortto remove the air bubbles visible at this stage of the process. Thiscauses the pigment sheet to stretch varying amounts in differentdirections so that it is difficult and sometimes impossible to securelater the exact registration of the three pigment sheets that isrequired in the iinished print. The

time involved not only representswaste but as'. the time required forsqueegeeing the three 'ditferent gelatin prints may be different, thetime control of the processing of the three prints is entirely disruptedand is reflected in the :Il nal print.

The application of pressure in connection with this step in the processis highly important.`

While mechanical pressing means andV weights, such as marble slabs, havebeen employed. they are not only difllcult to handle but are alsodilllcut to manipulate to secure the uniform pressure that is requiredfor the best prints. Where marble slabs are used, two or three slabsabout "Vg" thick are usually employed, .the pressure obtained therebybeing in the order of 0.3# per square inch. Even when perfectly planesurfaces are provided in the press and the pressure is applied withabsolute uniformity, which is virtually impossible with the devices nowin use, the best prints cannot be secured because of irregularities inthe other elements making up the sandwich such as the plastic, thepigmented gelatin and the paper. Such irregularitiescause unequaldistribution of pressure to the extent that double the intended pressuremay be applied in some spots and only one-half the pressure in otherspots.

The drying of the prints at this stage is also important as it has beenfound that they must be brought to approximately a predetermined watercontent before they are washed, else the resultant images are notsatisfactory.

Similar problems as to air bubbles, pressure. and drying arise inconnection with the transfer of the three registered pigment sheets fromthe temporary support to the nal support. Heretofore considerable timehas been required for the vigorous squeegeeing necessary to remove theair bubbles and for the nal drying and difficulty has been experiencedin securing even an approximate uniform pressure.

In overcoming the aforesaid disadvantages. it is an object of` myinvention to provide novel methods and means wherein steps such as theforegoing can be carried out in a much shorter time than has beenpossible heretofore and with better results. I

Still a further object of my invention is the provision .,of novelmethods and means wherein the steps of removing the air bubbles,reducing the moisture content, and applying uniform pressure can beperformed simultaneously in the above procedure and in similar processeswith assurance as to the final results.

1n the drawing:

Figure 1 is an exploded view of my invention as embodied in anarrangement for simultaneously de-aerating. drying and pressing apigment print onto a sheet oi plastic.

Figure 2 is a section taken through one endof the flexible blanket of myinvention illustrating the ridge or dam which is provided to insureairtight contact with the supporting base.

Figure 3 isa section through the vacuum connection to the exibleblanket. l

Figure 4 is av partialsecuon taxen on the une 4 4 of Figure 5,illustrating the manner in which the flexible blanket embraces theedgesr ofthe Y sheets thereunder.

Figure 6 is a section ora modified table top wherein a groove is formedin the table top to receive the sealing dam on the blanket.

The present invention involves the use of a base member for supportingthe prints which are to be pressed, dried and deaerated for transfer orlike purposes, and a blanket or cover of flexible air-tight materialsuch as soft rubberwhich is placed over the prints with its sides incontact as a table l I having' a substantially plane smooth` top surfaceI2 is provided. Taking the step ofl transferring a pigment print onto asheet of plastic by way of illustration, a plastic sheet is shown at 'I3and pigment print at I4, the pigmented gelatin being on the underside ofthe print. Plastic sheet I3 is contacted with pigment print I4, the twolaid upon table I I and a blanket I5 of exible air-tight material suchas soft rubber placed over the assembled sheets. Blanket I5 is providedwith a ridge or dam I6 on its underside and adjacent its edges which isarranged to contact surface I2 of table II outside the area of theplastic sheet and the pigment print as shown in Figure 4 and provide asurrounding air-tight seal. To facilitate the forming of the seal, thetop of table II maybe formedwith a shallow groove I2' (Fig. 6) ofv aconfiguration corresponding to that of dam I6 and into which the lowerportion of the dam may be tted when the unit is assembled. y

` To connect the underside of blanket I5 to a source of vacuum such as aconventional aspirator 2| arranged to be operated by city water pressureand a hose connection 22, the blanket is formed with a hole I5 boundedon the upper side of the blanket by a small flange I1 on one end of aconnection I1 arranged to receive hose connection 22. A ring 20 .ofsmaller inside diameter than the outside diameter of flange I1' is ittedover connection I1 and suitably sealed to the upperside of blanket I5 byrubber cement as shown at I8. To prevent localization of the vacuumeffective through connection I'I and the possible sealing of the innerend of hole I5', a sheet I9 of porous material such as cloth is appliedto the underside of the blanket and cemented thereto only about itsedges. It is preferred to extend the cloth or like porous material overthe entire of dam I5 and seal it to the blanket around its edges only.The provision of such a porous memberlin-eures the access ,of vacuum toall parts of the surface immediately adjacent the blanket, despite theconnection of the vacuum at only one point. In lieu of a porousmaterial. the underside of the rubber blanket may be slightly roughened.In operation, the assembly presents the appearance -shown in Figure 5wherein it will be noted that blanket I5 is drawn'down around its edgesso that it conforms closely to the outline of the underneath sheets. Byreason-of this conformation ofthe blanket, a channel 23 (Fig. 4) isformed around the periphery oi the sheet of plastic and the pigmentsheet so that the vacuum beneath the blanket is effective completelyaround the periphery of the-contacted sheets. As blotters or similarporous sheets are usually placed between table II and sheet I3 as wellas between blanket I5 and pigment print I4, the vacuum is effectivethrough the porous sheets onl all surfaces of the contacted plastic andpigment sheet, this being further assured by porous material I9.

This vacuum not only tends to reduce the moisture to the correct amountfor the subsequent washing and to remove the air bubbles but alsooperates to cause the lblanket to press the print and plastic sheettogether with uniform pressure over their entire areas. The pressureobtainable with the well-known aspirator and citywater pressure will runat least 12 lbs. per square inch which is equal to a pile of marbleabout l0 feet highVv or a pile of steel about 42" high. Such pressure isobtainable with a vacuum of about l25" Hg. In some cases, it has beenfound possible to secure a vacuum of as high as 28" Hg. with the samemeans and consequently secure a higher pressure.

Wherev it has heretofore been necessary toV (as is obtainable with threemarble slabs of the type usually employed) or more, it is possible withrthe invention to eliminate squecgeeing except what is actuallynecessary to bring the pigment and plastic sheet into contact andsimultaneously dry to the desired degree, de-aerate and press with thedesired degree of pressure within the period of 10 minutes. As threepigment sheets must be treated in each processing, this results in asaving of time in excess of 45 minutes for this step alone. Moreover asall the sheets are given uniform treatment for the same period` of time,uniform results are assured and there is no disruption of the timeschedule. It has been found in practice that the present inventionbrings the water content downto the requisite degree of dampness for thesubsequent washing with hot water and it is not necessary to requiredapproximately 40 minutes and the application of the considerablepressure to secure a satisfactory transfer. With the treatment of thetemporary support andthe final support 'by the method of this inventionand the application of vacuum of the order that can be obtained withunderside ofthe blanket within the boundaries city water pressure and aconventional aspirator.

i. e., 25" to 28" Hg., it has been found p0Siib1e to cut this time downto 10 minutes and secure better results.

Thus in the tri-color pigment process for a single print, it has beenfound possible to save in excess of 1 hr. and 15 minutes in actual timein addition to the time and labor involved in the squeegeeing hithertoconsidered necessary in an attempt to remove the air bubbles, and theadditional apparatus required to secure what was hoped to be the desireduniform pressure.'

In the over-al1 process it has been found possible to save as much asthree to four and onehalf hours and at the same time improve thecharacter of the prints produced and eliminate any possibility ofimperfections due to air bubbles, the application of non-uniformpressure, imper fect register or improperI drying.

Having described my invention, I claim:

An improvement in the art of tri-color pigment printing wherein a sheetsupporting a transferable image and a receiving medium to receive theimage are brought together in face to face relation to form a, sandwichand then processed to remove water and air from the sandwich and toeffect the transfer of the image to the receiving medium comprising:placing the sandwich on a planar air-impervious supporting surface;placing an airtight exible blanket over the sandwich to form, incooperation with the support, a sealed chamber enclosing the sandwich;and evacuating the chamber to withdraw air and moisture from thesandwich and to cause the blanket to press the sandwich uniformly andfirmly against the support to effect the transfer of the image.

CHARLES W. WILLIAMS.

